This invention relates generally to plastic components for lamps, and more particularly to plastic headlamp components formed from multiple resins having different heat distortion temperatures.
A variety of thermoplastic materials are available in the marketplace for use in automotive lighting systems. A basic criterion for material selection in lighting systems is the heat distortion temperature of the material. In general, the higher the heat distortion temperature, the higher the cost of the thermoplastic. The heat distortion temperature is the temperature at which the components begin to soften and distort under a specified force. If the component is a headlamp reflector, the temperature experienced by the reflector can be affected by design considerations such as reflector diameter, bulb diameter, bulb depth, lens depth, spacer depth and reflector depth.
One problem that has been observed is that some metallized thermoplastic lamp components, when heated to temperatures close to their heat distortion temperature become hazy in appearance which affects the performance and/or aesthetics of the lamp component. Also, some unmetallized thermoplastics can distorted unacceptably when heated above their heat distortion temperature. Using thermoplastics having higher heat distortion temperature characteristics to form the entire component can sometimes alleviate the problem. However, higher heat distortion temperature materials are generally more expensive and can exhibit undesirable flow characteristics which can affect molding operations.